Dispensers of high viscosity fluids may require significant force input from the user in order to initiate dispensing. Pushing downward with the palm of one's hand has been found to be an ergonomically efficient way for a user to develop sufficient force to dispense high viscosity fluids, such as toothpaste. Positive displacement pumps which utilize this approach have become available recently. An example is the MENTADENT.TM. toothpaste co-dispenser, a Trademark of Chesebrough-Pond's USA Co. of Greenwich, Conn.; which is disclosed in U.S. Pat. Nos. 5,295,615, and 5,335,827 to Gentile. The Mentadent co-dispenser has an upper portion containing two cylinders, each filled with different components of a toothpaste. At the end of each cylinder is a piston frictionally engaged in its cylinder to prevent leakage of toothpaste fluid from the cylinder. The upper portion is telescopingly connected to a bottom portion having two upright posts of equal length, which are spaced apart so as to align with the cylinders of the upper portion. When a user presses downward on the upper portion, the pistons are pressed against the two fixed posts. Such pressure causes the pistons to move upward into the cylinders and to drive toothpaste fluids from each cylinder through separate discharge orifices connected to the top of the cylinders. The amount of fluid dispensed from each cylinder is determined by the distance the upper portion is pushed downward and the diameters of the two cylinders.
The MENTADENT positive displacement toothpaste dispenser suffers from several deficiencies. First, the pistons provide considerable frictional resistance to movement in the cylinders when they are tight enough to prevent fluid leakage. High static friction and high fluid yield point require users to press hard to initiate dispensing. As a result, hard pressing to initiate flow must be immediately followed by lighter pressing to control displacement in order to avoid dispensing too much fluid. Such control is difficult for many users. Second, piston and cylinder arrangements require accurately molded or machined parts for adequate fit and reproducible operation. Such part accuracy is expensive.
A dispenser which avoids static friction and the need for accurate part requirements offers better function and lower manufacturing costs. In the caulking gun art, others have attempted to solve a similar friction problem by placing one or more flexible fluid-containing bags against a movable ram. For example, U.S. Pat. No. 3,323,682 to Creighton, Jr., et al. shows a ram pressed against the closed end of two side-by-side bags. The ram crushes the bags and fluid is dispensed from the opposite end of the bags. That is, each bag wrinkles axially as it shortens in length. Thin bags can be crushed nearly flat. However, even bag crushing may provide frictional resistance to dispensing because as the bag is crushed, the wrinkles typically slide along the cylinder wall. Also, any cocking of the ram relative to the cylinder may cause the bag wrinkles to jam between the ram and the cylinder wall.
Another type of toothpaste dispenser is the Crest Neat Squeeze dispenser, a trademark of The Procter & Gamble Company of Cincinnati, Ohio; which is disclosed in U.S. Pat. No. 4,842,165 to Van Coney. A squeezebottle has a fluid-containing bag housed inside the squeezebottle along with one-way air and fluid valving. Together these elements enable air pressure to be developed inside the squeezebottle and outside the bag which causes the bag to invert and thereby push out the toothpaste from the bag. An inverting bag has minimal friction resistance because the bag wall behaves like a rolling diaphragm. That is, the fold at the inverting point progressively moves from the closed end of the bag toward the discharge end. Such a dispenser can also be designed to discharge virtually all of its contents if the closed end of the bag matches the shape of the inside of the discharge end of the dispenser.
The Crest Neat Squeeze dispenser is a single use dispenser. When empty, the entire dispenser is discarded. Squeezebottles with bags and valving are more expensive than conventional toothpaste tubes. Thus, there is value in reusing the squeezebottle with its valving and in replacing fluid-containing bags in order to reduce the average package cost per unit of fluid delivered. Replacement bags are difficult to manage with such a dispenser, however, because the dispenser utilizes trapped air for dispensing. Reestablishing an air-tight seal after bag replacement is a problem because every user cannot be depended upon to provide adequate sealing. For example, when an expensive threaded engagement between rigid components is provided to generate a seal, users do not torque the components to the same degree.
U.S. Pat. No. 5,305,920 to Reiboldt et al. shows a Crest Neat Squeeze dispenser having a replacement cartridge with threaded components at the base of the dispenser. U.S. Pat. 5,454,486 to Mack et al. shows a similar dispenser having threaded components at the top of the dispenser. In both references not only is there an air sealing issue, but also there is a hygiene issue associated with toothpaste. Toothpaste is known for unsanitary-looking residue buildup on nozzles of tubes. The shape of the Crest Neat Squeeze nozzle is designed to minimize such buildup, but users still prefer a new nozzle with each new container of toothpaste. Replacing the nozzle with the bag results in the discharge valve also being replaced.
Therefore, what is missing in the prior art is a dispenser which utilizes the low friction of an inverting bag, and which has a replacement bag & nozzle that avoids both a discharge valve being discarded with each nozzle and unreliable user-generated air-tight sealing.
Dispensing multiple fluid components in accurate proportions is also an important need. Such fluid components typically have to be kept apart until the time of dispensing to prevent premature reaction between them. Vacuum type pump dispensers and dual compartment tubes are readily available. However, differences in fluid rheology cause one fluid to flow differently than the other when such dispensers are actuated. As a result, proportions dispensed are often inaccurate. One fluid reservoir may even run out of fluid before the other. Positive displacement pumps for simultaneous dispensing of multiple fluids in accurate proportions are now available, such as the MENTADENT piston and cylinder dispenser, whose deficiencies are discussed hereinbefore.
It is an object of the present invention to provide replaceable fluid cartridges having inverting bag reservoirs for high viscosity fluids, which operate in positive displacement co-dispensers such that there is the least possible pressing force required of a user to co-dispense fluids.
It is another object of the present invention to provide an inexpensive fluid cartridge, having a nozzle with separate orifices for each fluid and a nozzle closure, which can be made by an economic process from only three parts.